(1) The appellate authority or the revisional authority may at any time within three years from the date of an order passed by it on appeal or revision, as the case may be, and the assessing authority may at any time within three years from the date of any assessment or order passed by it, of its own motion, rectify any mistake apparent from the record of the appeal, revision, assessment or order, as the case may be, and shall, within the like period, rectify any such mistake which has been brought to its notice by an assessee:
Provided that no such rectification shall be made which has the effect of enhancing an assessment or reducing a refund unless the assessee has been given a reasonable opportunity of being heard in the matter.
(2) Where any such rectification has the effect of reducing an assessment, the assessing authority shall make any refund which may be due to such assessee.
1[(3) Where any such rectification has the effect of enhancing an assessment or reducing a refund, the assessing authority shall serve on the employer or on the other person, a notice of demand in the prescribed form and such sum shall be payable by such employer or the other person, as the case may be, within such time, at such place and to such person, as may be specified in such notice.]